U.S. patent application number 15/308532 was filed with the patent office on 2017-06-15 for ink composition.
This patent application is currently assigned to Hewlett-Packard Development Company, L.P.. The applicant listed for this patent is Hewlett-Packard Development Company, L.P.. Invention is credited to Vladimir Jakubek, Richard J. McManus, Sundar Vasudevan.
Application Number | 20170166765 15/308532 |
Document ID | / |
Family ID | 54767121 |
Filed Date | 2017-06-15 |
United States Patent
Application |
20170166765 |
Kind Code |
A1 |
McManus; Richard J. ; et
al. |
June 15, 2017 |
INK COMPOSITION
Abstract
An ink composition includes colorant, hydroxylated and
non-hydroxylated co-solvents, and water. A weight percent ratio of
hydroxylated to non-hydroxylated co-solvents ranges from 46:54 to
about 62:38. The composition also includes an acid and a
polyurethane copolymer binder. The acid is selected from the group
consisting of oleic acid, linoleic acid, undecanoic acid,
dodecanoic acid, tridecanoic acid, and combinations thereof. The
binder is formed from the polymerization of a diisocyanate and at
least three diols including a first diol containing a hydrophilic
stabilizing group, and a second diol having less than 8 atoms in a
backbone chain between two hydroxyl groups. A mole percentage of
the second diol is at least 30% of a total mole percentage of diol
monomers in the binder. An acid number of the binder ranges from 50
to 75. The composition also includes lithium present in an amount
ranging from about 50 to about 400 ppm.
Inventors: |
McManus; Richard J.;
(Corvallis, OR) ; Vasudevan; Sundar; (Corvallis,
OR) ; Jakubek; Vladimir; (Corvallis, OR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hewlett-Packard Development Company, L.P. |
Houston |
TX |
US |
|
|
Assignee: |
Hewlett-Packard Development
Company, L.P.
Houston
TX
|
Family ID: |
54767121 |
Appl. No.: |
15/308532 |
Filed: |
June 6, 2014 |
PCT Filed: |
June 6, 2014 |
PCT NO: |
PCT/US2014/041368 |
371 Date: |
November 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 11/102 20130101;
C09D 11/36 20130101; C09D 11/38 20130101; B41J 2/17503 20130101;
C09D 11/324 20130101 |
International
Class: |
C09D 11/36 20060101
C09D011/36; C09D 11/102 20060101 C09D011/102; B41J 2/175 20060101
B41J002/175; C09D 11/38 20060101 C09D011/38 |
Claims
1. An ink composition, comprising: a colorant; a hydroxylated
co-solvent; a non-hydroxylated co-solvent, wherein a weight percent
ratio of the hydroxylated co-solvent to the non-hydroxylated
co-solvent in the ink composition ranges from 46:54 to about 62:38;
an acid selected from the group consisting of oleic acid, linoleic
acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and
combinations thereof; a polyurethane copolymer binder formed from
the polymerization of a diisocyanate and at least three diols
including a first diol containing a hydrophilic stabilizing group,
and a second diol having less than 8 atoms in a backbone chain
between two hydroxyl groups, wherein a mole percentage of the
second diol is at least 30% of a total mole percentage of diol
monomers in the polyurethane copolymer binder, and wherein an acid
number of the polyurethane copolymer binder ranges from 50 to 75;
lithium present in an amount ranging from about 50 ppm to about 400
ppm; and water.
2. The ink composition as defined in claim 1 wherein: the
hydroxylated co-solvent is selected from the group consisting of
2-methyl-1,3-propanediol, 2-hydroxyethyl-2-pyrrolidinone,
2-ethyl-2-hydroxymethyl-1,3-propanediol, di-(2-hydroxyethyl)-5,
5-dimethylhydantoin, glycerol, diethylene glycol, triethylene
glycol, tripropylene glycol, tetraethylene glycol,
dipropyleneglycol, 3-methyl-1,3-butanediol,
3-methyl-1,5-pentanediol, 1-(2-hydroxyethyl)-2-imidazolidinone,
1,6-hexanediol, 1,5-pentanediol, and combinations thereof; and the
non-hydroxylated co-solvent is selected from the group consisting
of 2-pyrrolidinone, sulfolane, diethyleneglycol dimethyl ether, and
combinations thereof.
3. The ink composition as defined in claim 2, excluding: any other
co-solvents; and acids chosen from stearic acid, elaidic acid,
linolenic acid, saturated fatty acids having a carbon chain of
fewer than 11 carbons, and saturated fatty acids having a carbon
chain of more than 13 carbons.
4. The ink composition as defined in claim 1 wherein: the
isocyanate is selected from the group consisting of
1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate
(IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene
diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI),
4,4'-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane
diisocyanate (H.sub.12MDI), 3,3'-dimethyl-4,4'-biphenyl
diisocyanate (TODD, dodecane diisocyanate (C.sub.12DI),
1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene
diisocyanate (TMXDI), 1,4-benzene diisocyanate,
trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate;
the first diol is selected from the group consisting of dimethylol
acetic acid, 2,2'-dimethylol butanoic acid, 2,2'-dimethylol
propionic acid (DMPA), and 2,2'-dimethylol butyric acid; and the
second diol is selected from the group consisting of
1,2-propanediol, 1,3-propanediol, ethylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, neopentyl glycol,
2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and
combinations thereof.
5. The ink composition as defined in claim 4 wherein the at least
three diols include one diol from the group of the first diol and
two diols from the group of the second diol.
6. The ink composition as defined in claim 4 wherein the at least
three diols further includes one diol from the group of the first
diol, one diol from the group of the second diol, and a third diol
i) having a formula OH--R--OH, wherein R is selected from the group
consisting of a polyether, a polyester, a polycarbonate, a
polycarbonate-co-polyester, and an acrylic, or ii) having a formula
OH--R.sup.4--OH, wherein R.sup.4 is a C.sub.1-C.sub.7 alkyl, or a
C.sub.6-C.sub.40 aryl, or a C.sub.9-C.sub.40 aryl substituted by
C.sub.1-C.sub.10 alkyl.
7. The ink composition as defined in claim 4 wherein a number
average molecular weight of the polyurethane copolymer binder
ranges from about 3500 to about 10,000.
8. The ink composition as defined in claim 1 wherein: the
hydroxylated co-solvent is present in an amount ranging from about
9 wt % to about 14.5 wt % of the total wt % of the ink composition;
the non-hydroxylated co-solvent is present in an amount ranging
from about 9 wt % to about 10.5 wt % of the total wt % of the ink
composition; and the weight percentage of each of the hydroxylated
co-solvent and the non-hydroxylated co-solvent is selected to
satisfy the weight percent ratio.
9. The ink composition as defined in claim 1 wherein the
hydroxylated co-solvent is 2-methyl-1,3-propanediol, and the
non-hydroxylated co-solvent is 2-pyrrolidinone, and the weight
percent ratio is about 50:50.
10. The ink composition as defined in claim 1 wherein the
hydroxylated co-solvent is 2-hydroxyethyl-2-pyrrolidinone, and the
non-hydroxylated co-solvent includes a combination of
2-pyrollidinone and sulfolane, and the weight percent ratio is
about 56:44.
11. The ink composition as defined in claim 1 wherein: the colorant
is chosen from self-dispersed pigments, polymer dispersed pigments,
dyes, and combinations thereof; the colorant is present in an
amount ranging from about 2 wt % to about 6.5 wt % of a total wt %
of the ink composition; a polyurethane copolymer binder is present
in an amount ranging from about 1.0 wt % to about 3.0 wt % of the
total wt % of the ink composition; and the acid is present in an
amount ranging from about 0.03 wt % to about 1.0 wt %.
12. A print cartridge, comprising: a fluid reservoir; a fluid
ejector in fluid communication with the fluid reservoir; a nozzle
in fluid communication with the fluid ejector; an ink composition
present in the fluid reservoir, the ink composition including: a
colorant present in an amount ranging from about 2.0 wt % to about
6.0 wt % of a total wt % of the ink composition; a hydroxylated
co-solvent; a non-hydroxylated co-solvent, wherein a weight percent
ratio of the hydroxylated co-solvent to the non-hydroxylated
co-solvent in the ink composition ranges from 46:54 to about 62:38;
an acid selected from the group consisting of oleic acid, linoleic
acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and
combinations thereof; a polyurethane copolymer binder formed from
the polymerization of a diisocyanate and at least three diols
including a first diol containing a hydrophilic stabilizing group,
and a second diol having less than 8 atoms in a backbone chain
between two hydroxyl groups, wherein a mole percentage of the
second diol is at least 30% of a total mole percentage of diol
monomers in the polyurethane copolymer binder, and wherein an acid
number of the polyurethane copolymer binder ranges from 50 to 75,
the polyurethane copolymer binder present in an amount ranging from
about 1.0 wt % to about 3.0 wt % of the total wt % of the ink
composition; lithium present in an amount ranging from about 50 ppm
to about 400 ppm; and water; and an anti-evaporative layer present
at an interface between air and the ink composition in an orifice
of the nozzle, the anti-evaporative layer formed during uncapped
non-use, thereby reducing evaporation of the water from the ink
composition.
13. The print cartridge as defined in claim 12 wherein: the
hydroxylated co-solvent is selected from the group consisting of
2-methyl-1,3-propanediol, 2-hydroxyethyl-2-pyrrolidinone,
2-ethyl-2-hydroxymethyl-1,3-propanediol, di-(2-hydroxyethyl)-5,
5-dimethylhydantoin, glycerol, diethylene glycol, triethylene
glycol, tripropylene glycol, tetraethylene glycol,
dipropyleneglycol, 3-methyl-1,3-butanediol,
3-methyl-1,5-pentanediol, 1-(2-hydroxyethyl)-2-imidazolidinone,
1,6-hexanediol, 1,5-pentanediol, and combinations thereof; and the
non-hydroxylated co-solvent is selected from the group consisting
of 2-pyrrolidinone, sulfolane, diethyleneglycol dimethyl ether, and
combinations thereof.
14. The print cartridge as defined in claim 12 wherein: the
isocyanate is selected from the group consisting of
1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate
(IPDI), trimethylhexamethylene diisocyanate (TMDI), 2,4-toluene
diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI),
4,4'-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane
diisocyanate (H.sub.12MDI), 3,3'-dimethyl-4,4'-biphenyl
diisocyanate (TODD, dodecane diisocyanate (C.sub.12DI),
1,5-naphthalene diisocyanate (NDI), m-tetramethylene xylylene
diisocyanate (TMXDI), 1,4-benzene diisocyanate,
trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene diisocyanate;
the first diol is selected from the group consisting of dimethylol
acetic acid, 2,2'-dimethylol butanoic acid, 2,2'-dimethylol
propionic acid (RMPA), and 2,2'-dimethylol butyric acid; the second
diol is selected from the group consisting of 1,2-propanediol,
1,3-propanediol, ethylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,2-hexanediol, neopentyl glycol,
2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and
combinations thereof; and the at least three diols further include
a third diol having a formula OH--R--OH, where R is selected from
the group consisting of a polyether, a polyester, a polycarbonate,
a polycarbonate-co-polyester, and an acrylic.
15. A method for improving capped recovery performance of an ink
composition having a high solids content, the method comprising:
selecting a polyurethane copolymer binder formed from the
polymerization of a diisocyanate and at least three diols including
a first diol containing a hydrophilic stabilizing group, and a
second diol having less than 8 atoms in a backbone chain between
two hydroxyl groups, wherein a mole percentage of the second diol
is at least 30% of a total mole percentage of diol monomers in the
polyurethane copolymer binder, and wherein an acid number of the
polyurethane copolymer binder ranges from 50 to 75; selecting a
hydroxylated co-solvent; selecting a non-hydroxylated co-solvent;
and incorporating a weight percent ratio of the hydroxylated
co-solvent to the non-hydroxylated co-solvent into a mixture, the
weight percent ratio of the hydroxylated co-solvent to the
non-hydroxylated co-solvent ranging from about 46:54 to about
62:38, and the mixture including: from about 0.03 wt % to about 1.0
wt % of an acid selected from the group consisting of oleic acid,
linoleic acid, undecanoic acid, dodecanoic acid, tridecanoic acid,
and combinations thereof; from about 2.0 wt % to about 6.5 wt % of
a colorant; from about 1.0 wt % to about 3.0 wt % of the
polyurethane copolymer binder; from about 4.5 wt % to about 9.0 wt
% of a combination of the colorant and the polyurethane copolymer
binder; from about 50 ppm to about 400 ppm of lithium; and a
balance of water.
Description
BACKGROUND
[0001] Inkjet printing or recording systems are commonly used as an
effective way to produce images on a print medium, such as paper.
Generally, ink droplets are ejected from a nozzle by the inkjet
printing system and onto the print medium to produce an image
thereon. Examples of inkjet printing systems include thermal inkjet
printers and piezoelectric inkjet printers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0002] Features and advantages of examples of the present
disclosure will become apparent by reference to the following
detailed description and drawings, in which like reference numerals
correspond to similar, though perhaps not identical,
components.
[0003] FIG. 1 is an enlarged, cutaway, cross sectional, perspective
semi-schematic illustration of an example of a print cartridge
including an example of the ink composition disclosed herein;
[0004] FIG. 2 is a flow diagram illustrating an example of a method
according to an example of the present disclosure; and
[0005] FIGS. 3A through 3I illustrate capped recovery performance
of example inks of the present disclosure and comparative example
inks.
DETAILED DESCRIPTION
[0006] Examples of the ink composition disclosed herein exhibit
desirable print quality, print reliability, and decap performance
(thereby maintaining good nozzle health). With many inkjet inks, it
is difficult to simultaneously achieve all of these attributes. For
example, inks having a relatively high solids content (e.g.,
pigment and/or polymer/binder loading) for improved image optical
density and durability may exhibit poor print reliability. For
another example, inks having a lower solids content for improved
print reliability and decap performance may result in images with
poor optical density and/or durability.
[0007] The term "print reliability," as used to herein, generally
refers to the ability of a print cartridge or pen to recover and
successfully print after being stored capped for some extended
period of time. During capped storage, the colorant in the ink may
settle out of the dispersed state and plug the nozzle(s) of the
print cartridge. Also during capped storage, the polymer/binder,
alone or in combination with the colorant, may form a plug locally
within the nozzle. If nozzles are completely plugged, the print
cartridge may be rendered useless. It has been found that blocked
nozzles may be skewed towards one end of the print cartridge (e.g.,
the lower end if the cartridge is stored on an angle/tilt, e.g.,
5.degree.). The skewed failure may be due to settling colorant.
Capped storage has also been found to lead to random nozzle failure
throughout the print cartridge (i.e., nozzle failure is not
concentrated to one particular area of the cartridge). Random
nozzle failure may be due to locally formed binder or binder and
colorant plugs.
[0008] The term "decap performance," as referred to herein, means
the ability of the inkjet ink to readily eject from the printhead,
upon prolonged exposure to air. The decap time is measured as the
amount of time that a printhead may be left uncapped before the
printer nozzles no longer fire properly, potentially because of
clogging, plugging, or retraction of the colorant from the drop
forming region of the nozzle/firing chamber. The length of time a
thermal inkjet pen can remain unused and uncapped before spitting
would be required to form an acceptable quality ink drop is called
decap time, or first drop decap time. Another decap metric is the
number of spits required to get the pen healthy at a specific time
interval. The longest decap time that would give acceptable first
drop quality or the fewest number of spits required at any given
decap time would be desirable for any given ink.
[0009] Generally, as water evaporates from an ink formulation, the
percentage of organic components in the ink increases. As the ink
becomes more enriched in the organic co-solvents and other
nonvolatile components, a colorant (e.g., a dispersed pigment)
therein which is strongly hydrophilic is pulled back/retracted into
the bulk of the aqueous phase.
[0010] Examples of the present disclosure control the degree/rate
of pigment retraction in an efficient and cost-effective manner.
Pigment retraction is referred to herein as "pigment ink vehicle
separation" (PIVS).
[0011] As pigmented ink dries in an inkjet printhead, a rapid PIVS
may take place (e.g., within about 1-4 seconds), which may result
in the nozzles and/or the ink channel being substantially devoid of
the colorant. As such, a rapid rate of PIVS is generally
undesirable because of the idle (or decap) time being too short. To
address PIVS, inkjet printers may force the printhead to spit onto
a special absorbing pad/spittoon on a regular basis after a period
of idle time (e.g., a predetermined number of spits per nozzle at a
given frequency may maintain nozzle health of idle nozzles during
printing). The rate of spitting is substantially controlled by the
rate of PIVS. Very frequent spits are generally undesirable,
because ink is consumed during spitting, and printing is slowed
down.
[0012] In contrast, a slow rate of PIVS (e.g., from about greater
than 4 seconds to about 60 seconds) is generally beneficial for the
printhead functioning, for example, when the printhead is stored in
an uncapped position, because it prevents the undesirable clogging
of the nozzles or retraction of the colorant from the nozzle.
Further, in some instances, it may be desirable for a print system
to exhibit very slow PIVS (e.g., from greater than a minute to
several hours).
[0013] Further, examples of the ink composition according to the
present disclosure also provide improved decap performance for
dye-based inks. In the case of both pigment-based and dye-based
previously known inks, as water evaporates, a viscous plug may form
at the nozzle in some instances. A subsequent ink drop would have
to be fired through this viscous plug, and as such, the first few
drops may not be ejected/ejected appropriately out of the orifice.
Depending on the ink, successful ejection may occur after a couple
of firing events. In contrast, examples of the ink composition of
the present disclosure appear to prevent formation of this viscous
plug (in pigment-based or dye-based inks), as well as controlling
PIVS (in pigment-based inks).
[0014] Examples of the ink composition disclosed herein include
components that provide excellent print reliability and decap
performance. In addition, the ink composition includes a high
solids content, and thus forms prints with a desirable optical
density and durability. "High solids content," as used herein,
refers to the total weight percent of the combination of a colorant
and a polyurethane copolymer binder in the ink composition. In an
example, the high solids content ranges from about 4.5 wt % to
about 9.0 wt % of the total wt % of the ink composition.
[0015] In particular, the ink composition disclosed herein includes
a combination of a particular polyurethane copolymer binder and a
particular co-solvent system. It is believed that the binder and
the co-solvent system interact with each other and with the
colorant in a manner that enables a relatively high solids
loading/content to be included without deleteriously affecting the
print reliability. The co-solvent system includes a combination of
one solvent that had previously been found to contribute to blocked
nozzles skewed towards one end of the print cartridge and another
solvent that had previously been found to contribute to random
nozzle failure. In the examples disclosed herein, the combination
of these two solvents unexpectedly results in an ink composition
that does not exhibit either blocked nozzles skewed towards one end
of the print cartridge or random nozzle failure.
[0016] In addition, the ink composition disclosed herein may be
suitable for use with any inkjet printing system (e.g., thermal,
piezoelectric). For example, the ink composition may be printed
with an inkjet printer having a drop frequency ranging from about 2
kHz to about 36 kHz. As such, the ink composition may be printed
with a high speed inkjet printer (an example of which has a drop
frequency ranging from about 24 kHz to about 36 kHz).
[0017] In the examples disclosed herein, the ink composition
includes the colorant, the co-solvent system, an acid, the
polyurethane copolymer binder, lithium, and a balance of water.
Other additives, such as a biocide or a non-ionic surfactant may
also be added to the ink composition.
[0018] The colorant may be any of self-dispersed pigments, polymer
dispersed pigments, dyes, and combinations thereof.
[0019] Carbon blacks may be used as the colorant in examples of the
present ink composition. For example, carbon blacks may be used
that are of the lamp black, furnace black or gas black type. These
carbon blacks may be made water dispersive: through oxidation,
either through the carbon black process or through post carbon
black manufacturing treatment (e.g., by ozonation); by reaction of
the carbon black surface with either small molecule, oligomeric or
polymeric materials that are water soluble or dispersive in nature
(e.g., p-aminobenzoic acid, acrylic based oligomers or polymers
made of monomers such as acrylic or methacrylic acid and esters
thereof, and/or polyurethane oligomers or polymers). These carbon
blacks may also be made dispersive in water through adsorption of
oligomers or polymers of the previously mentioned acrylic,
methacrylic, or polyurethane compositions. Carbon blacks can be
further made dispersive through encapsulation of the pigment with a
latex polymer composed of, e.g., acrylic acid, acrylic esters,
methacrylic acid, methacrylic esters, styrene or vinyl acetate.
These materials can be made dispersive through the inclusion of
various functional groups (such as carboxylates, sulfonates,
phosphates or ethylene oxide derivatives) within the polymer.
[0020] Some suitable self-dispersed carbon blacks, as well as
polymer dispersed pigments are commercially available from E.I. du
Pont de Nemours and Co. (Wilmington, Del.), Sensient Technologies
Corporation (Milwaukee, Wis.), and Cabot Corporation (Boston,
Mass.).
[0021] Other pigments with no limitation on color or chemical
composition can be used, some examples of which include PY74,
PY155, PY128, PY185, PR122, PR254, PR178, PV19, PB15:2, PB15:3, and
PB15:4. These colorants can also be made dispersive in water by
various means such as small molecule, oligomeric or polymeric
attachment, through adsorption of oligomeric or polymeric
materials, or through encapsulation (e.g., as described for carbon
black).
[0022] Any suitable dyes may be used in examples of the present ink
composition.
[0023] In the examples disclosed herein, the colorant is present in
an amount ranging from about 2 wt % to about 6.5 wt % of the total
wt % of the ink composition. In another example, the colorant is
present in an amount ranging from about 4 wt % to about 4.5 wt % of
the total wt % of the ink composition. It is to be understood that
the colorant, along with the polyurethane copolymer binder, makes
up the high solids content of the ink composition. In an example,
the colorant loading and the polyurethane copolymer binder loading
are selected so that the total (high) solids content of the ink
composition ranges from about 4.5 wt % to about 9.0 wt % of the
total weight percent of the ink composition. Any suitable amount of
the colorant and/or binder within the given ranges may be selected
as long as the total (high) solids content of the ink composition
ranges from about 4.5 wt % to about 9.0 wt %. Examples of the
polyurethane copolymer binder amount are described below.
[0024] The co-solvent system disclosed herein includes a
hydroxylated co-solvent and a non-hydroxylated co-solvent. The
weight percent ratio of the hydroxylated co-solvent to the
non-hydroxylated co-solvent ranges from 46:54 to about 62:38. In an
example, the ink composition includes from about 9 wt % to about
14.5 wt % of the hydroxylated co-solvent, and from about 9 wt % to
about 10.5 wt % of the non-hydroxylated solvent. The respective
weight percent is selected so that the weight percent ratio of
hydroxylated to non-hydroxylated co-solvents is in accordance with
the range provided herein. In some examples, the hydroxylated
solvent is present in an amount that is greater than the
non-hydroxylated solvent. Furthermore, it is to be understood that
no other solvents are included in the ink composition.
[0025] Examples of the hydroxylated co-solvent include
2-methyl-1,3-propanediol, 2-hydroxyethyl-2-pyrrolidinone,
2-ethyl-2-hydroxymethyl-1,3-propanediol (EHPD) (also known as
trimethylolpropane), di-(2-hydroxyethyl)-5, 5-dimethylhydantoin
(commercially available as DANTOCOL.RTM. DHE from Lonza, Inc.,
Allendale, N.J.), glycerol, diethylene glycol, triethylene glycol,
tripropylene glycol, tetraethylene glycol, dipropyleneglycol,
3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol,
1-(2-hydroxyethyl)-2-imidazolidinone, 1,6-hexanediol,
1,5-pentanediol, and combinations thereof.
[0026] Examples of the non-hydroxylated co-solvent include
2-pyrrolidinone, sulfolane, diethyleneglycol dimethyl ether, and
combinations thereof.
[0027] One specific example of the co-solvent system includes
2-methyl-1,3-propanediol as the hydroxylated co-solvent and
2-pyrrolidinone as the non-hydroxylated co-solvent. In this
example, the weight percent ratio of
2-methyl-1,3-propanediol:2-pyrrolidinone is about 50:50. Another
specific example of the co-solvent system includes
2-hydroxyethyl-2-pyrrolidinone as the hydroxylated co-solvent, and
a combination of 2-pyrollidinone and sulfolane as the
non-hydroxylated co-solvent. In this example, the weight percent
ratio of 2-hydroxyethyl-2-pyrrolidinone:the combination of
2-pyrollidinone and sulfolane is about 56:44.
[0028] As mentioned above, examples of the ink composition also
include lithium, and an acid (e.g., a fatty acid surfactant) chosen
from oleic acid (i.e., cis-octadec-9-enoic acid, having one cis
double bond), linoleic acid (two cis double bonds), undecanoic
acid, dodecanoic acid, tridecanoic acid, and combinations
thereof.
[0029] The fatty acid surfactant has a carboxylate head and a long
alkyl tail. It appears that the carboxylate group aids in
contributing to good decap. In addition, the alkyl tail has one or
two cis double bonds. It has been discovered that the corresponding
fully saturated fatty acids with 14 carbons or more, or those with
trans double bonds generally do not provide the same benefit for
enhancing decap performance. As such, examples of the ink
composition of the present disclosure exclude acids chosen from
stearic acid (a fully saturated fatty acid with 18 carbons),
elaidic acid (the trans isomer of oleic acid), linolenic acid
(three cis double bonds), linear (as opposed to branched) saturated
fatty acids having a carbon chain of fewer than 11 carbons, and
linear saturated fatty acids having a carbon chain of more than 13
carbons, and combinations thereof.
[0030] In an example, the chosen acid is dodecanoic acid (also
known as lauric acid).
[0031] The acid is present in an amount ranging from about 0.03 wt
% to about 1.0 wt % of the total wt % of the ink composition.
[0032] It is to be understood that the lithium may be present in
the composition as an ion in solution, or as a lithium salt of the
acid. As an example, the lithium may be added to the ink
composition in the form of a number of its salts, for example,
lithium chloride, lithium bromide, lithium iodide, lithium
hydroxide, lithium acetate, lithium benzoate, lithium nitrate, or
combinations thereof. However, lithium carbonate is generally not
desirable; as it appears to degrade decap performance in some
instances.
[0033] Further, other alkali metals, e.g., sodium and/or potassium,
may be present in examples of the ink composition. However, it is
to be understood that the lithium aids in forming an
anti-evaporative layer; whereas other alkali metals that may be
present do not function to aid in formation of the anti-evaporative
layer, nor do they hinder formation of the anti-evaporative
layer.
[0034] The binder used in the ink composition disclosed herein is a
polyurethane copolymer binder formed from the polymerization of a
diisocyanate and at least three diols. In an example, the at least
three diols include a first diol containing a hydrophilic
stabilizing group, and one or more of a second diol having less
than 8 atoms in a backbone chain between two hydroxyl groups (which
leads to the formation of a short hard segment (shown in formula
(IV) below)). In another example, the at least three diols include
the first diol, the second diol, and a third diol having a formula
OH--R--OH, wherein R is selected from the group consisting of a
polyether, a polyester, a polycarbonate, a
polycarbonate-co-polyester, and an acrylic. In yet another example,
the at least three diols include the first diol, the second diol,
and a third diol having a formula OH--R.sup.4--OH, where "R.sup.4"
is defined in formula IV below. As examples, R.sup.4 may be a
C.sub.1-C.sub.7 alkyl, or a C.sub.6-C.sub.40 aryl, or a
C.sub.9-C.sub.40 aryl substituted by C.sub.1-C.sub.10 alkyl.
Examples of each of the diols are provided below.
[0035] In the examples disclosed herein, the polyurethane copolymer
binder is formed from the reaction of isocyanate and diols, and
thus includes hard and soft segments. The hard segment is the
segment in between and including two adjacent carbamate groups. The
soft segment is formed from high molecular weight diols or polyols.
A soft segment is mobile and may be present in a coiled formation.
The urethane groups on one polymer chain form hydrogen bonds with
the same or similar groups on neighboring polymer chains, resulting
in a polyurethane network. In many instances, a soft continuous
phase surrounds a hard semi-crystalline region in a polyurethane
network.
[0036] In the polyurethane, the hard segment is covalently coupled
to a soft segment. Adjusting the hard and soft segments can provide
the polyurethane copolymer with a desired level of elasticity and
toughness. In many polyurethanes, ionizable groups are incorporated
into the hard segment to render the polyurethane water dispersible.
However, ionizable groups can interfere with the inter-molecular
hydrogen bonding, and thus in the examples disclosed herein,
ionizable groups are not included in at least the short hard
segments (e.g., see formula (IV) below) of the resulting
polyurethane copolymer. This strengthens the polyurethane
copolymer. Separation of ionizable groups from the short hard
segment can also lead to better control of the acid content while
reducing the time for semi-crystalline region formation, which in
turn reduces the dry-time.
[0037] In the examples disclosed herein, the ratio of the
isocyanate to diol is greater than 1:1. In an example, the ratio of
isocyanate to diol ranges from about 1.05:1 to about 1.5:1.
[0038] In an example, the polyurethane copolymer binder has the
following structure:
##STR00001##
wherein each of Q.sup.1, Q.sup.2, and Q.sup.3 is independently
selected from
##STR00002##
as long as Q.sup.1, Q.sup.2, and Q.sup.3 contain at least one of
(II), at least one of (III), and at least one of (IV). In (II),
(III), and/or (IV), the following are applicable: [0039] each
R.sup.1 is C.sub.1-C.sub.20 alkyl, C.sub.3-C.sub.20 substituted
alkyl, C.sub.3-C.sub.10 cycloalkyl, C.sub.3-C.sub.20 substituted
cycloalkyl, or C.sub.6-C.sub.40 aryl or C.sub.9-C.sub.40
substituted aryl from a diisocyanate; [0040] each R.sup.2 is
independently C.sub.3-C.sub.20 substituted alkyl, C.sub.3-C.sub.20
substituted cycloalkyl, or C.sub.9-C.sub.40 substituted aryl;
[0041] each R.sup.3 is independently C.sub.9-C.sub.20 alkyl,
C.sub.9-C.sub.20 alkyl substituted by C.sub.1-C.sub.10 alkyl or
C.sub.6-C.sub.15 aryl, C.sub.9-C.sub.40 aryl or C.sub.9-C.sub.40
aryl substituted by C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.20
aryl, or --(R.sup.11--O--R.sup.10--O--R.sup.11)--; or
HO--R.sup.3--OH is a diol incorporating polyether, polyester,
polycarbonate, polycarbonate-co-polyester, or acrylic; [0042] each
R.sup.4 is independently C.sub.1-C.sub.7 alkyl, C.sub.3-C.sub.20
alkyl substituted by C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.15
aryl, C.sub.6-C.sub.40 aryl or C.sub.9-C.sub.40 aryl substituted by
C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.20 aryl, provided that the
backbone atoms on R.sup.4 forming a chain linking the two oxygen
atoms in (IV) are less than 8; [0043] n, m and p are integers from
1 to 200; [0044] the capping agent is one or more members selected
from the group consisting of R.sup.5CHR.sup.6OH,
R.sup.5CHR.sup.6SH, R.sup.6R.sup.7NH, H--(OR.sup.8).sub.q--OH, and
epoxide CH.sub.2OCR.sup.6R.sup.7; [0045] each R.sup.5 is H,
C.sub.1-C.sub.20 alkyl, C.sub.3-C.sub.20 alkyl substituted by
C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.15 aryl, C.sub.6-C.sub.40
aryl or C.sub.9-C.sub.40 aryl substituted by C.sub.1-C.sub.10 alkyl
or C.sub.6-C.sub.20 aryl; [0046] each R.sup.6 is H,
C.sub.1-C.sub.20 alkyl, C.sub.6-C.sub.40 aryl or --R.sup.9OR.sup.8;
[0047] each R.sup.7 is H, --R.sup.9OR.sup.8, C.sub.1-C.sub.20
alkyl, C.sub.3-C.sub.20 alkyl substituted by C.sub.1-C.sub.10 alkyl
or C.sub.6-C.sub.15 aryl, C.sub.6-C.sub.40 aryl or C.sub.9-C.sub.40
aryl substituted by C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.20
aryl, provided that when R.sup.6 is H, R.sup.7 is not H; [0048]
R.sup.6 and R.sup.7 can be taken together with the nitrogen atom to
form a cyclic amine or substituted cyclic amine with an O or S atom
replacing a C atom on said cyclic amine; [0049] each R.sup.8 is
C.sub.1-C.sub.20 alkyl or C.sub.6-C.sub.20 aryl; [0050] each
R.sup.9 is C.sub.1-C.sub.20 alkyl, C.sub.3-C.sub.20 alkyl
substituted by C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.15 aryl;
[0051] each R.sup.10 is independently C.sub.4-C.sub.20 alkyl,
C.sub.4-C.sub.20 alkyl substituted by C.sub.1-C.sub.10 alkyl or
C.sub.6-C.sub.15 aryl, C.sub.9-C.sub.40 aryl or C.sub.9-C.sub.40
aryl substituted by C.sub.1-C.sub.10 alkyl or C.sub.6-C.sub.20
aryl; [0052] each R.sup.11 is independently C.sub.1-C.sub.20 alkyl,
C.sub.4-C.sub.20 alkyl substituted by C.sub.1-C.sub.10 alkyl or
C.sub.6-C.sub.15 aryl; and [0053] q is an integer from 1 to 20.
[0054] In the examples disclosed herein, the isocyanate is a
diisocyanate. Suitable diisocyanates may be selected from the group
consisting of 1,6-hexamethylene diisocyanate (HDI), isophorone
diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI),
2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate
(2,6-TDI), 4,4'-diphenylmethane diisocyanate (MDI),
4,4-dicyclohexylmethane diisocyanate (H.sub.12MDI),
3,3'-dimethyl-4,4'-biphenyl diisocyanate (TODD, dodecane
diisocyanate (C.sub.12DI), 1,5-naphthalene diisocyanate (NDI),
m-tetramethylene xylylene diisocyanate (TMXDI), 1,4-benzene
diisocyanate, trans-cyclohexane-1,4-diisocyanate, and 4,6-xylyene
diisocyanate.
[0055] Some examples of the first diol, which includes a
hydrophilic stabilizing group and ultimately forms part of the
monomer with Formula (II), include dimethylol acetic acid,
2,2'-dimethylol butanoic acid, 2,2'-dimethylol propionic acid
(DMPA), and 2,2'-dimethylol butyric acid.
[0056] Some examples of the second diol, which has less than 8
atoms in the backbone chain between two hydroxyl group and
ultimately forms part of the monomer with Formula (IV), include
1,2-propanediol, 1,3-propanediol, ethylene glycol, 1,4-butanediol,
1,5-pentanediol, 1,6-hexanediol, 1,2-hexanediol, neopentyl glycol,
2-methyl-1,3-propanediol, 3-methyl-1,5-pentane diol, and
combinations thereof.
[0057] When included, examples of the third diol have a hydrophobic
segment and ultimately form part of the monomer with Formula (III).
Some examples of this third diol have the formula OH--R--OH,
wherein R is selected from the group consisting of a polyether, a
polyester, a polycarbonate, a polycarbonate-co-polyester, and an
acrylic. Other examples of the third diol have the formula
OH--R.sup.4--OH. R.sup.4 may be any of the examples previously
given, such as a C.sub.1-C.sub.7 alkyl, or a C.sub.6-C.sub.40 aryl,
or a C.sub.9-C.sub.40 aryl substituted by C.sub.1-C.sub.10
alkyl.
[0058] Any suitable method that reacts the isocyanate with the at
least three diols may be used to form the polyurethane copolymer.
The previously mentioned capping agent may be added when it is
desirable to terminate the polymerization. The amount of the
capping agent employed should be approximately equivalent to the
unreacted isocyanate groups in the prepolymer. The ratio of active
hydrogens from amine groups in the chain terminator to isocyanate
groups in the prepolymer are in the range from about 1.0:1 to about
1.2:1, or from about 1.0:1.1 to about 1.1:1, or from about 1.0:1.05
to about 1.1:1, on an equivalent basis.
[0059] In the final polyurethane copolymer binder, the mole
percentage of the second diol is at least 30% of a total mole
percentage of diol monomers in the polyurethane copolymer binder.
The acid number of the polyurethane copolymer binder ranges from 50
to 75, and the number average (M.sub.n) molecular weight of the
polyurethane copolymer binder ranges from about 3,500 to about
10,000. In another example, the M.sub.n of the polyurethane
copolymer binder ranges from about 5,000 to about 8,500.
[0060] The amount of the polyurethane copolymer binder that is
included in the ink composition may range from about 1 wt % to
about 3 wt % of the total wt % of the ink composition. In another
example, the amount of the polyurethane copolymer binder ranges
from about 1.7 wt % to about 2.0 wt %. As mentioned above, the
colorant loading and the polyurethane copolymer binder loading are
selected so that the total (high) solids content of the ink
composition ranges from about 4.5 wt % to about 9.0 wt % of the
total weight percent of the ink composition. Any suitable amount of
the colorant and/or binder within the given ranges may be selected
as long as the total (high) solids content of the ink composition
ranges from about 4.5 wt % to about 9.0 wt %.
[0061] Examples of the ink composition of the present disclosure
may further include an additive chosen from non-ionic surfactants,
biocides, and combinations thereof.
[0062] When a non-ionic surfactant is utilized, a suitable amount
of the non-ionic surfactant may range from about 0.05 wt % to about
2 wt %. Some specific examples of the non-ionic surfactant that may
be used in the ink composition disclosed herein include acetylene
diols, bis-tartrate esters, 1,2-hexanediol, mono alcohols,
N-alkylpyrrolidinones, and combinations thereof. One example of the
acetylene diol is SURFYNOL.RTM. 104, available from Air Products
and Chemicals, Inc., Allentown, Pa. Examples of suitable
bis-tartrate esters include diisoamyl tartrate, dibutyl tartrate,
dibenzyl tartrate, and diisopropyl tartrate. Some examples of
suitable mono alcohols include lauryl alcohol (i.e., 1-dodecanol),
oleyl alcohol (i.e., octadec-9-en-1-ol), stearyl alcohol (i.e.,
1-octadecanol), and combinations thereof. Examples of the
N-alkylpyrrolidinone are N-octylpyrrolidinone and
N-dodecylpyrrolidinone. Some commercially available
N-alkylpyrrolidinones include SURFADONE.RTM. LP-100
(octylpyrrolidinone) and SURFADONE.RTM. LP-300
(dodecylpyrrolidinone), both of which are available from Ashland
Inc. In one example, the non-ionic surfactant is selected so that
it does not include any ethyleneoxy groups.
[0063] When a biocide is utilized, a suitable amount of the biocide
may range from about 0.05 wt % to about 0.5 wt %. It is to be
understood that the upper limit for the biocide(s) may depend upon
the type of biocide and its toxicological effect and/or regulatory
requirements. Suitable biocides include, for example, PROXEL.TM.
GXL, KORDEK.TM. MLX (The Dow Chemical Co.), BIOBAN.TM. CS-1246 (The
Dow Chemical Co.) and/or ACTICIDE.RTM. B20 and/or M20 (Thor
GmbH).
[0064] In any of the examples disclosed herein, a balance (up to
100 wt %) of the composition is water.
[0065] The pH of examples of the ink composition generally ranges
from about 7 to about 11. It may be desirable that the ink
composition have a basic pH, ranging anywhere from greater than 7
to 12. When the initial pH of the resulting ink composition is
acidic, neutral, or near-neutral basic (e.g., having a pH ranging
from 7.1 to 8), it may be desirable to adjust the pH of the
resulting ink composition to a basic or more basic pH. Any suitable
base may be added to adjust the pH, as long as the added base does
not interfere with the other desirable properties of the ink
composition. Some examples of suitable bases include NaOH or KOH.
The amount of base added will depend, at least in part, on the
initial pH of the ink composition and the desired final pH of the
ink composition. In an example, the pH is adjusted from about 9 to
about 10, and a suitable amount of base is added until this pH is
obtained.
[0066] It has been found that lithium salt(s) of the fatty acid(s)
in the examples of the ink composition of the present disclosure
form an anti-evaporative layer during uncapped non-use at an
interface between the air and the ink composition in an orifice of
a nozzle, thereby reducing evaporation of the water from the ink
composition. In examples of the present ink composition, the
anti-evaporative layer is observed (with an optical microscope)
forming by about 2 seconds of uncapped non-use. However, it is
believed that formation of the layer begins sooner than 2 seconds
of uncapped non-use.
[0067] Referring now to FIG. 1, a print cartridge is generally
depicted at 10. The print cartridge 10 includes a housing 12 (which
may include one or more layers of different materials) that is
operatively connected to a reservoir 14 that contains an example of
the ink composition 20 disclosed herein. A fluid path/ink channel
24 connects the reservoir 14 to a fluid ejector 16. In a thermal
inkjet print cartridge, the fluid ejector 16 is a heating element
that creates heat to vaporize the ink composition 20, which creates
a bubble that expands to push the ink composition 20 (in the form
of drops 22) out of an orifice 26 of a nozzle 18 that is aligned
with the fluid ejector 16. While a single fluid ejector 16 and
nozzle 18 is shown, it is to be understood that a single print
cartridge 10 may include multiple (e.g., 400 or some other
desirable number) fluid ejectors 16 and nozzles 18. While not
shown, it is to be understood that the print cartridge 10 includes
an integrated circuit that routes signals (e.g., from a processor
that is capable of running suitable computer readable instructions)
to the desirable fluid ejector(s) 16 and nozzle(s) 18 for firing
ink drops 22 therefrom to produce images on a desirable medium.
[0068] The print cartridge 10 is representative of a single nozzle,
and it is to be understood that a single print cartridge includes
many nozzles. When included in a high speed inkjet printing system
including a page wide array, it is to be understood that several
print cartridges 10 (i.e., dies), each of which includes at least
1,000 nozzles, are arranged together. While not shown, it is to be
understood that the high speed inkjet printing system may also
include an automated service station. This service station may be
programmed to ensure that the print cartridge 10 is automatically
capped, decapped, and cleaned with minimal system downtime. This
also contributes to enhanced print quality.
[0069] As mentioned above, lithium salts of the fatty acid(s) in
the examples of the ink composition 20 form an anti-evaporative
layer during uncapped non-use at an interface I between air and the
ink composition 20 in the orifice 26 of the nozzle 18, thereby
reducing evaporation of the water from the ink composition 20.
[0070] Referring now to FIG. 2, an example of a method for
improving capped recovery performance of the ink composition 20
according to the present disclosure is generally depicted at 200.
The method 200 includes selecting a polyurethane copolymer binder
formed from the polymerization of a diisocyanate and at least three
diols including a first diol containing a hydrophilic stabilizing
group, and a second diol having less than 8 atoms in a backbone
chain between two hydroxyl groups, wherein a mole percentage of the
second diol is at least 30% of a total mole percentage of diol
monomers in the polyurethane copolymer binder, and wherein an acid
number of the polyurethane copolymer binder ranges from 50 to 75,
as shown at reference numeral 202. The method 200 also includes
selecting a hydroxylated co-solvent (reference numeral 204) and
selecting a non-hydroxylated co-solvent (reference numeral
206).
[0071] As shown at reference numeral 208, the method 200 also
includes incorporating a weight percent ratio of the hydroxylated
co-solvent to the non-hydroxylated co-solvent (ranging from about
46:54 to about 62:38) into a mixture, including from about 0.03 wt
% to about 1.0 wt % of an acid selected from the group consisting
of oleic acid, linoleic acid, undecanoic acid, dodecanoic acid,
tridecanoic acid, and combinations thereof; from about 2.0 wt % to
about 6.5 wt % of a colorant; from about 1.0 wt % to about 3.0 wt %
of the polyurethane copolymer binder; from about 4.5 wt % to about
9.0 wt % of a combination of the colorant and the polyurethane
copolymer binder; from about 50 ppm to about 400 ppm of lithium;
and a balance of water.
[0072] Examples of the ink composition of the present disclosure
have a relatively high solids content, and thus form high quality
and durable prints. The colorant, binder, and co-solvent system
enable the high solids content without deleteriously affecting the
print reliability of the ink composition.
[0073] To further illustrate the present disclosure, examples are
given herein. It is to be understood that these examples are
provided for illustrative purposes and are not to be construed as
limiting the scope of the present disclosure.
Example
[0074] Four example inks (Inks C, F, G, and H) including a
polyurethane copolymer binder and the co-solvent system disclosed
herein were prepared. Five comparative inks (Inks A, B, D, E, and
I) including a polyurethane copolymer binder but not including the
co-solvent system disclosed herein were also prepared. The
polyurethane copolymer binder in comparative inks A, B, and I and
in ink C was formed from the reaction of isophorone diisocyanate
(IPDI) with 1,3-propanediol, hydroquinone bis(2-hydroxyethyl)ether
(HQEE), and dimethylol propionic acid (DMPA). The polyurethane
copolymer binder in comparative inks D and E and inks F--H was
formed from the reaction of isophorone diisocyanate (IPDI) with
1,3-propanediol, 1,2-propanediol, and dimethylol propionic acid
(DMPA).
[0075] The formulations of the inks and comparative inks are shown
in Table 1. The amounts are given in weight percents. The balance
of each of the inks and comparative inks was water.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Comp. Comp. Component Ink
A Ink B Ink C Ink D Ink E Ink F Ink G Ink H Ink I Carbon black 4.5
4.5 4.5 4.4 4.4 4.4 4.4 4.4 4.5 dispersion 2- 18 0 9 0 0 0 3.5 8.8
13 pyrrolidinone** 2-methyl-1,3- 0 18 9 0 0 0 0 0 0 propanediol*
Lauric acid 0.18 0.18 0.18 0.24 0.24 0.24 0.24 0.24 0.18 HE2P* 0 0
0 14.7 16.7 13.2 13.2 13.2 0 Sulfolane** 0 0 0 8.7 8.7 10.5 7 1.7
1.7 SURFYNOL 0 0 0 0.05 0.05 0.05 0.05 0.05 0.05 104 .RTM.
SURFADONE 0 0 0 0.05 0.05 0.05 0.05 0.05 0 LP-100 .RTM. Oleic
acid** 0 0 0 0.02 0.02 0.02 0.02 0.02 0 Polyurethane 2 2 2 1.7 1.7
1.7 1.7 1.7 2 copolymer binder 3-methyl-1,3- 0 0 0 0 0 0 0 0 5
butanediol* Silicone based 0 0 0 0 0 0 0 0 0.01 surfactant (BYK
348)*** Hydroxylated/ 0/100 100/0 50/50 63/37 66/34 56/44 56/44
56/44 25/75 non- hydoxylated co-solvent weight percent ratio
*indicates that the solvent is hydroxylated **indicates the solvent
is non-hydroxylated ***from BYK Chemie
[0076] Ink cartridges filled with comparative inks A and B and Ink
C were stored capped for 8 weeks. After the 8 week period, the inks
were printed to test for capped recovery. Nozzle pattern prints
were produced by jetting the above described ink compositions, on a
"HP Recycled paper" with COLORLOK.RTM. Technology for office
applications, using an HP Cartridge 940 in an HP Office Jet Pro
8000 printer. It is to be understood that the various nozzle
patterns were printed on the first page of printing after
storage.
[0077] The results for these comparative inks A and B and ink C are
shown in FIGS. 3A through 3C, respectively. As shown in FIG. 3A,
comparative ink A (with no hydroxylated co-solvent) exhibited
blocked nozzles that were skewed towards one end of the print
cartridge. As shown in FIG. 3B, comparative ink B (with no
non-hydroxylated co-solvent) exhibited random nozzle failure. As
shown in FIG. 3C, ink C (50:50 weight percent ratio of hydroxylated
to non-hydroxylated co-solvents) exhibits excellent capped
recovery.
[0078] Ink cartridges filled with comparative inks D, E, and I and
inks F, G, and H were stored capped for 4 weeks. After the 4 week
period, the inks were printed in the same manner described above to
test for capped recovery. The results for these comparative inks D,
E, and I are shown in FIGS. 3D, 3E, and 3I, respectively. The
results for these inks F, G, and H are shown in FIGS. 3F, 3G, and
3H, respectively. As shown in FIG. 3D, comparative ink D (63:37
weight percent ratio of hydroxylated to non-hydroxylated
co-solvents) exhibited random nozzle failure. As shown in FIG. 3E,
comparative ink E (66:34 weight percent ratio of hydroxylated to
non-hydroxylated co-solvents) exhibited random nozzle failure. As
shown in FIGS. 3F, 3G, and 3H, inks F, G, and H (56:44 weight
percent ratio of hydroxylated to non-hydroxylated co-solvent)
exhibited 6 or less random nozzle failures. As shown in FIG. 3I,
comparative ink I (25:75 weight percent ratio of hydroxylated to
non-hydroxylated co-solvents) exhibited blocked nozzles that were
skewed towards one end of the print cartridge (i.e., the bottom of
each column did not print).
[0079] Each of the comparative inks and inks included a high solids
content (greater than 6 wt % carbon black dispersant and
polyurethane copolymer binder). Those including the co-solvent
system disclosed herein exhibited excellent capped recovery.
[0080] Reference throughout the specification to "one example",
"another example", "an example", and so forth, means that a
particular element (e.g., feature, structure, and/or
characteristic) described in connection with the example is
included in at least one example described herein, and may or may
not be present in other examples. In addition, it is to be
understood that the described elements for any example may be
combined in any suitable manner in the various examples unless the
context clearly dictates otherwise.
[0081] It is to be understood that the ranges provided herein
include the stated range and any value or sub-range within the
stated range. For example, a range of 50 ppm to about 400 ppm
should be interpreted to include not only the explicitly recited
limits of 50 ppm to about 400 ppm, but also to include individual
values, such as 53 ppm, 104.25 ppm, 350 ppm, etc., and sub-ranges,
such as from about 150 ppm to about 375 ppm, from 125 ppm to about
300 ppm, etc. Furthermore, when "about" or "substantially" is
utilized to describe a value, this is meant to encompass minor
variations (up to +/-10%) from the stated value.
[0082] In describing and claiming the examples disclosed herein,
the singular forms "a", "an", and "the" include plural referents
unless the context clearly dictates otherwise.
[0083] While several examples have been described in detail, it is
to be understood that the disclosed examples may be modified.
Therefore, the foregoing description is to be considered
non-limiting.
* * * * *